In cataract surgery the OVD is an important tool. The OVD maintainsthe anterior chamber depth, protects the corneal endothelium,and facilitates implantation of the IOL. Differences in concentrationand molecular mass of the viscoelastic components of OVDs leadto different physico-chemical characteristics, which are reflectedin anterior chamber maintenance and retention capacity. Thisstudy was designed to measure the result in force required todeliver marketed OVDs as OVSs that require high or uneven expulsionforces could result in less control when used in clinical practice.

Methods:

The expulsion force was measured for several commercial OVDs.The expulsion force tests were performed on a Lloyd LRX Pluspull tester set at compression mode. The measurements were performedwith a 50 N loading cell and speed was set to expel 3 ml/min.For all products tested its own delivery system was used. Settingsused for speed were between 52-171 mm/min and the length ofpiston movement set between 12-20 mm. Zero shear has been measuredfor all of the mentioned commercial products.

Results:

The results were on average between 16 and 24 N. For most productsthe expulsion force was the same during emptying the syringe.However, one product, Dispersive OVD 1, showed an early peakbefore going back to lower forces. Dispersive OVD 2 showed anincreasing force throughout the test.

Conclusions:

There are significant differences in force required to expelOVDs from their delivery system including maximum force requiredand changes in force over the entire delivery.